1. Field of the Invention
This invention relates to a novel guide system for the gripper drive tape in a shuttleless loom which enables the sley to move even when said tape is still cooperating with its guide mounted on said sley, without affecting the guiding conditions and while still ensuring self-positioning of the lower warp yarns of the shed and effective guiding of said tape within said shed, so as to enable a higher operating rate and productivity to be obtained from the loom and the possibility of constructing looms of greater weaving width.
2. Discussion of the Background
As is well known, in shuttleless looms, a giver gripper, starting from one side of the loom, generally inserts the weft yarn into the open shed formed by the warp yarns, until it transfers it to a taker gripper which carries it outside said shed on the opposite side of the loom. Said two grippers are each driven by an insertion tape to the ends of which the gripper is fixed. The insertion tape is supported and guided in its travel within the shed by a suitable guide member.
Various types of tape guide members are already known in the art.
One of these consists substantially of a continuous guide track mounted on the loom sley and extending along approximately the entire weaving width.
Such a continuous tape guide has, however the drawback that the tapes with their grippers must necessarily slide by pressing on the bed of lower warp yarns of the shed which, when the shed is open, cannot do anything other than rest against said guide, resulting in sometimes undesirable contact. Again, to prevent any deflection of said lower warp yarns of the shed about that edge of the continuous guide on the reed side being able to damage the yarns by rubbing caused by the movement of the sley and hence of said guide, a further member has to be used for supporting said warp yarns in order to prevent said contact.
Said drawbacks are eliminated in another known type of tape guide member, consisting substantially of a plurality of guide teeth fixed spaced apart on said loom sley in such a manner that the two sides of each tape can slide within guide grooves formed by said teeth.
With this latter guide the teeth can freely pass through the lower warp yarns of the shed and hence support the tapes and their grippers without these coming into contact with said warp yarns. However, this type of guide member also has drawbacks, the main one of which is that it does not allow relative movement between the gripper tape and the guide teeth in the direction of the warp yarns so that, specifically in a loom in which the tape drive wheels are mounted on the fixed loom frame and hence do not move with the sley, it is absolutely impossible to move said sley when tapes are still cooperating with the guide grooves of said teeth, this however being essential in modern looms to achieve ever increasing operating speeds. A further drawback is the possibility that, during movement, the grooves of said guide teeth can engage both the warp and weft yarns, with their consequent deterioration or breakage.
It is sought to remedy these latter drawbacks by another type of tape guide member which, although consisting of a plurality of guide teeth fixed spaced apart on the loom sley and extending through the lower warp yarns of the shed when said shed is open, slidingly supports said tapes not by means of grooves but by means of uninterrupted flat upper surfaces provided at the summit of said teeth, which extend parallel to the lower warp yarns of said shed.
In this case there is evidently no further danger of engaging the weft and/or warp yarns and moreover said flat support surfaces, which extend parallel to the lower warp yarns of the shed, enable the guide teeth to move relative to the gripper tapes in the direction of the warp yarns, hence enabling the sley, which is rigid with said teeth, to move when the tapes are still resting on said flat surface of the teeth.
This latter relative movement is, however, accompanied by a change in the guiding conditions of the tapes in that the rotation of the sley and consequently of the flat support surfaces of said guide teeth means that said surfaces are not parallel to the tapes, so that the contact regions between said surfaces and the tapes are considerably reduced, with a consequent increase in the wear of the tapes and of the guide teeth, and in addition, during the stage in which said surfaces assume positions of continuously decreasing distance from the theoretical side plane of said tapes, said surfaces generate deleterious thrusts upwards on said tapes, with consequent increase in their wear.
A further drawback of the tape guide system comprising a plurality of teeth with flat upper surfaces is the fact that the warp yarns which remain arranged obliquely on said flat surfaces of the teeth are inevitably damaged or broken by the tape or by the relative gripper.
Finally, a further drawback is a lack of an effective tape guide for insuring optimum operation in the case of looms with a large weaving width.